Scarlet Monastery was great. I did my first Cathedral clear at about level 37 and at level 38 I was able to clear Cathedral, including both bosses, in under 30 minutes (though I did skip some pulls in the outdoor areas). Compared to Herod, the Cathedral bosses are a piece of cake because they don't do any AoE, just tank and damage deal, healing a couple times as necessary. I finally did manage to get Herod down without cheesing him but it takes a lot of effort on my part keeping everyone alive and out of his AoE.
After SM Cathedral... nothing. I went over to RFD and farmed that for a bit to get a few specific drops but it is the same level as Cathedral. Then I went over to Uldaman and cleared the first half, up to Lady Ironaya which is also the same level as Cathedral. I tried to push through to the second half of Uldaman and I was able to clear all but the last boss who is simply too high level. So, there I was level 42 and stuck. Uldaman is too high, SM Cathedral is too low. I ended up going to Zul'Farrak just clearing up to the first boss until level 43 and now I'm clearing up to the stair event which I will say is a lot of fun.
As to my character development, the class makeup I have is crazy in terms of damage output. Leader of the Pack (+5% crit), Battle Shout (+131 AP), Blessing of Might (+115 AP), Improved Leader of the Pack (+4% life regen on crit), Strength of Earth (+41 strength), Grace of Air (+49 agility), Flametongue Totem (+9 to +28 fire damage per swing). In the end I have about 700 attack power on each character and 20% crit chance on all but the warrior/paladin (no crit talents on them). The rogue, druid and shaman dish out a ton of damage and the paladin and warrior make for some great tanks together (warrior holds primary creep while paladin holds the rest).
My quest to level 5 World of Warcraft characters at the same time.